Autorun Python code on TFT

[davidcoton]

I have a Model B with an Adafruit TFT attached. It's going to be a heating controller in a church (if I ever manage to jump all the hurdles).

I've got code that runs on the display, but I'm having trouble getting it to autorun. I added to /etc/rc.local:

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python3 /home/python/heating.py &

which seems to start the code, but it promptly aborts, leaving the x screen running and showing an error in the (hdmi) text terminal:

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_tkinter.TclError: No display name and no $DISPLAY environment variable

I've used Linux for some time, but still have no idea how to set the name and/or env var in an appropriate place -- or how to find what the correct value should be. Any hints?

[broo0ose]

I'd add it to

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/etc/xdg/lxsession/LXDE/autostart

Back up the file, you can remove the other lines and add your command with an @ at the beginning. Have a look at the file and you'll understand what I mean

[davidcoton]

Thanks for the reply, but it doesn't work that way either. It will wait for a login on the console -- despite autologin having been enabled (at least I think it was). I can't even get LXDE to start reliably now. If I try starting my program from the console, I get the same problem as in the first post.

I'm getting very discouraged -- autostart ought to be a minor part of the project, but I'm going to waste all my available time on it. It has been three months since I last had any programming time and it looks like I will never get enough time to make it all work. We may have to find another control system instead of building one on RPi.

[broo0ose]

Have you used

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sudo raspi-config

to force gui mode rather than command line.
That should do the auto-login for you.

[latki8]

If it is of any help, I was interested in trying this out myself (tkinter, not heating controller). I agree the tkinter error is probably because there is no x environment, ie the python code is running on the basic console function, but I have followed what has been suggested above and it all works fine as far as I can see and even with no HDMI screen connected, the python tkinter code is still running. The only problem I have is that my Noobs SD card still has all the other OS on it and the boot process won't continue until I press escape - annoying, but I want to keep my options open for now. In case it isn't clear, I don't have an Adafruit screen either.